The present invention relates to saber saws. Various saber saws have been conventionally developed to cut or saw woody or steel materials or pipes in the housing or building construction sites or similar fields.
Conventional saber saws are basically classified into first and second types. According to a saber saw of the first type, a saw blade is reciprocated along a linear path. According to a saber saw of the second type, a saw blade is moved along an orbital path, for example, an elliptic path. The second type is also referred to as the orbital cutting type.
U.S. Pat. No. 3,945,120 discloses a vibration dampening and heat sink mechanism for a reciprocating hand-held saw which has a carrier guide with limited axial and radial movement positively controlled by an eccentric.
The conventional saber saws of the orbital cutting type, for example disclosed in U.S. Pat. No. 3,945,120 and in U.S. Pat. No. 3,461,732, are preferable to cut relatively soft material, such as woody members.
In general, reciprocative movement of the saber saws cause axial vibration. Providing a counterweight is effective to suppress such vibrations (refer to U.S. Pat. Nos. 5,025,562 and 5,555,626).
An object of the present invention is to provide a saber saw of the orbital cutting type which can operate properly even when a saw blade is inversely attached to a saber saw body while suppressing vibration.
In order to accomplish this and other related objects, the present invention provides a first saber saw comprising a housing for accommodating a motor. A driven shaft is rotatably supported by the housing and rotated by the motor. A plunger causes reciprocative motion with respect to the housing. A saw blade is attached to a front end of the plunger. A first motion converting mechanism, interposed between the driven shaft and the plunger, converts rotational motion of the driven shaft into the reciprocative motion of the plunger. A counterweight causes reciprocative motion with respect to the housing. A second motion converting mechanism, interposed between the driven shaft and the counterweight, converts the rotational motion of the driven shaft into the reciprocative motion of the counterweight. A pair of opposing tracks, formed on the counterweight, extend in a direction substantially parallel to a reciprocating direction of the plunger. Guide means of the plunger can reciprocate along one of the opposing tracks formed on the counterweight while a clearance is maintained between the guide means and the other track.
According to the first saber saw, it is preferable that a roller shaft is provided at a rear end of the plunger so as to extend in a direction normal to the reciprocating direction of the plunger. Swing rollers serving as guide means, rotatably supported at both ends of the roller shaft, roll along one of the opposing tracks formed on the counterweight.
Furthermore, the present invention provides a second saber saw comprising a housing for accommodating a motor. A driven shaft is rotatably supported by the housing and rotated by the motor. A plunger causes reciprocative motion with respect to the housing. A saw blade is attached to a front end of the plunger. A guide sleeve, holding the plunger, is hingedly supported about a pivot fixed to the housing so that the guide sleeve can swing in a direction normal to a reciprocating direction of the plunger. A first motion converting mechanism, interposed between the driven shaft and the plunger, converts rotational motion of the driven shaft into the reciprocative motion of the plunger. A counterweight causes reciprocative motion with respect to the housing. A second motion converting mechanism, interposed between the driven shaft and the counterweight, converts the rotational motion of the driven shaft into the reciprocative motion of the counterweight. A pair of opposing tracks, formed on the counterweight, extend in a direction substantially parallel to a reciprocating direction of the plunger. The plunger can reciprocate along one of the opposing tracks formed on the counterweight. A roller shaft is provided at a rear end of the plunger so as to extend in a direction normal to the reciprocating direction of the plunger. The roller shaft is inserted in an elongated hole opened on the guide sleeve. And, swing rollers, rotatably supported at both ends of the roller shaft, roll along one of the opposing tracks formed on the counterweight while maintaining a clearance between each roller and the other track.
According to the first and second saber saws of the present invention, it is preferable that the pair of opposing tracks are formed in an axially elongated groove of the counterweight and the swing rollers interpose between the opposing tracks so as to leave a predetermined clearance. Furthermore, the swing rollers are depressed on one of the opposing tracks formed on the counterweight when the saw blade receives a reaction force from a material to be cut during a cutting operation.